text:
Who has final say over an aircraft flight path?
This question got me thinking... if there was an emergency situation on a commercial airliner (let's say both engines have flamed out or something) and the pilot wants to do one thing (land in the sea), while ATC insists they try to turn around and land at  the airport... who has the final say?
Obviously the pilot is the one physically in control of the aircraft, but if he ignores ATC, believing his approach is the only safe approach and ends up killing half of the passengers in the process, would he be liable for 100% responsibility since he didn't listen to ATC?

The pilot has 100% responsibility for how, where and when to fly/land. The movies make it seem like pilots are just mindless drones, under the control of ATC.
In actual fact ATC are there as an aid to the pilot, helping stop big metal tubes from colliding with one another.
This was borne out (to some extent) on US Airways 1549 where ATC were advising the pilot he could aim for his nearest airfield. His skill and experience (and of course having a front-row seat!) told him he would not make it, and he took the action to ditch on the Hudson river - saving all on board. We will never know what the outcome would have been if he had followed ATC advice, but multiple trips in a simulator have told us it might not have ended so well.
Final say is ALWAYS, 100% of the time, with the PIC.

Well, we do know what would have happened. They simulated the event with multiple pilots and all that tried to land at the airport crashed on first attempt.

@Cloud While that gives us a pretty high confidence... there could be other factors that we just don't have enough information to simulate; that could have made the difference. Hell, even without hidden variables, people aren't the most consistent creatures; there's a chance everyone survived if they tried for an airfield.

@Delioth Of course, if no-one can make the landing in the sim, it becomes a lot harder to blame the pilot for not trying.

How does this work, practically? Capt. Sully is flying the plane, and trouble starts. ATC says "fly to airport X", Capt. Sully says "Can't, going to the Hudson."  Does ATC then just accept his decision the first time he says it, and goes from there and work how to get him to the Hudson safely? Or is there a dialogue/discussion/pushback, like ATC "No you're not, that's dangerous and airport X is so close!", Sully "Can't make it still, we're going to the Hudson", ATC "What about airport Y...", etc.?

@BruceWayne practically (and legally), the pilot has to make the call, and there's no reason for the ATC to try to hold a meeting about the decision over the radio during an emergency situation; time and attention are precious during an emergency, and everyone involved knows that.

@ErinAnne - Oh for sure, time is of the essence.  So in my made up exchange ("Capt. Sully, please land at airport X, it's close" // "No, I can't make it. I'm ditching in the Hudson"), is ATC's next action to just accept Capt. Sully's decision and go from there? Or is there a quick back and forth discussing options,etc.?

@BruceWayne In an emergency the controller's job is to keep other traffic out of the way and provide the pilot with any information he may need. Beyond that his job is to leave the pilots alone and let them do what they need to do. He's in a support role.

@BruceWayne Why make it up when you can read the transcript? :)

This has nothing to do with US1549. The ATC was never advising them anything either, just telling them the options, on explicit captain's question, and then the captain just said they can't make it anyway and they'll be in Hudson. The rule that pilot in command has both full responsibility and authority exists since the dawn of time. (and thanks for the transcript link, @Bob)

@JanHudec it was merely an example of where ATC might have advised a pilot of a course of action, but that the pilot can take whatever action he likes. It wasn't meant to be so contentious.

@Bob Thanks for that, great idea. I wonder how often ATC and pilots get into fights xD

@Jamiec, and they didn't. They only answered pilots question about their options. They never ever suggested anything. And that's totally correct. They know the pilot must judge it themselves.

@JanHudec I'm not understanding your comment. It was my understanding that ATC essentially gave some options. That's it. I never (meant to) imply they said what needed/should be done. That was sort of the point - ATC are there to advise only. They have no say it what should be done.

@Jamiec, you said “were advising the pilot to aim for his nearest airfield”, but they never did that. They only answered his direct question whether some options are available, but it was not an advice. It was merely an information.

@JanHudec ok, so I very slightly changed the wording to "ATC were advising the pilot he could aim for his nearest airfield" - is that more accurate do you think?

@Jamiec, I don't think the word “advised” is correct for anything they said. “Advise” implies recommendation and that it clearly was not.

Well, since you specifically say "emergency situation" (yes, all-engines flame-out definitely qualifies as an emergency)...
I'm going to refer to the US regulations, simply because those are among the easiest to find in English. I'm also willing to bet that most jurisdiction have similar legal texts in place, differing at most in details.
14 CFR §91.3(a) and (b) and §91.13 are the basic rules, which state that:

§91.3   Responsibility and authority of the pilot in command.
(a) The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft.
(b) In an in-flight emergency requiring immediate action, the pilot in command may deviate from any rule of this part to the extent required to meet that emergency.
§91.13   Careless or reckless operation.
No person may operate an aircraft (...) in a careless or reckless manner so as to endanger the life or property of another.

(There are two variants in §91.13, but they boil down to the same thing, so I summarized them above.)
Under normal (non-emergency) circumstances, pilots are required to comply with ATC instructions and clearances. Excerpted from §91.123:

§91.123   Compliance with ATC clearances and instructions.
(a) When an ATC clearance has been obtained, no pilot in command may deviate from that clearance unless an amended clearance is obtained, an emergency exists, or the deviation is in response to a traffic alert and collision avoidance system resolution advisory. However, except in Class A airspace, a pilot may cancel an IFR flight plan if the operation is being conducted in VFR weather conditions. When a pilot is uncertain of an ATC clearance, that pilot shall immediately request clarification from ATC.
(b) Except in an emergency, no person may operate an aircraft contrary to an ATC instruction in an area in which air traffic control is exercised.
(c) Each pilot in command who, in an emergency, or in response to a traffic alert and collision avoidance system resolution advisory, deviates from an ATC clearance or instruction shall notify ATC of that deviation as soon as possible.

In an emergency situation, §91.3(b) and §91.123(c) take precedence; notice the exception for emergency situations throughout most of the above. These basically boil down to, if there is an emergency, the pilots can do what they deem necessary in order to deal with that emergency in a safe and expedient manner. However, they do have to tell ATC about it, generally "as soon as possible" (as in §91.123(c)), and it's not a free pass to do anything at any time just because the pilots want to; pilots who exercise their emergency authority should expect getting a talking to after they land, once the emergency situation clearly no longer exists. Once ATC knows about the emergency, they can help, for example by providing vectors to an airfield or by vectoring other aircraft out of the way. Even if you're flying in uncontrolled airspace, ATC might still be able to provide things like traffic advisories. In an emergency, trust me, any reasonable pilot will take all the help they can get, however little, but it had better actually help. The standard litmus test for aviation radio still applies: does saying on the radio what I'm about to transmit help increase aviation safety? If not, then refrain.
So ATC can make suggestions, in the form of instructions and clearances, and under normal circumstances pilots are expected and required to comply with those; but if an emergency exists, the pilot is free to give ATC the proverbial finger by simply saying "unable" and telling ATC what they are going to do instead, and ATC has to simply live with that fact, provide the assistance they are able to, and ensure the safety of other aircraft in the area. Everything else can wait until the aircraft (singular or plural) involved are safely on the ground. About all it takes is the magic word "mayday" or "declaring emergency".
All that said, if an airplane suffers a complete loss of engine power, then that plane is going to intersect the ground in short order no matter what ATC says or does. So even if they somehow had the power to, ATC telling the pilots "no you can't" would be about as productive as to tell the moon to stop orbiting the Earth, in that they can say it all they want, but it's not going to change the outcome. Obviously the pilots are going to do everything in their power to avoid a crash landing, but if they can't fix the problem while still in the air, then it will become a problem on the ground in one manner or another. ATC insisting that the pilots do something else would, at best, be a distraction reducing the pilots' ability to deal with the emergency. Of course, if the pilots are about to do something like fly into a mountain that ATC can't vector out of the way, it might still be a good idea for ATC to recommend to the pilots of the stricken flight to make a turn...

Saying “unable” is actually unrelated to emergency. By it the pilot simply rejects a clearance following which (they think) would be out of safe flight envelope of their aircraft. It happens e.g. when the controller requests crossing certain point above or below some altitude and the pilot does not think they can climb or descend as fast at their current condition.

@JanHudec Right; I didn't mean to imply that the only situation in which one might say "Unable" is during an emergency, but rather that an emergency is one possible reason why one might be unable to comply with ATC instructions, or why one might feel that complying with ATC instructions is unsafe.

The pilot in control has the final authority. They also have the responsibility to comply with ATC instructions under normal circumstances. Emergency authorizes the pilot to operate how they believe necessary for safe operation of the aircraft.
If the pilot ends up causing an accident, that's what he will be responsible for. If deviating from ATC instructions was the reason, it may or may not be be considered negligence or error.
See the canonical question: Who has the higher authority, the pilot in command or ATC?


text:
What is the relationship between centre of gravity, centre of pressure and pitch?
Ok so I've got a couple of questions regarding CG, CP and pitch
1) When the aircraft is taking off, is the tail down force required to pitch up the aircraft high? Because the aircraft always has a natural tendency to pitch down.
2) When the aircraft increases its AoA, the CP moves forward (towards the leading edge). Does this mean it would go ahead of the CG or move closer
to the CG.

Reading the heated discussion between Robert and JZYL makes me sad. Both are right and still they cannot agree. Maybe a longer and more detailed description might help.

1) When the aircraft is taking off, is the tail down force required to pitch up the aircraft high? Because the aircraft always has a natural tendency to pitch down.

The aircraft should always have a natural tendency to return to its trimmed state. This might be by pitching up or down, depending on the actual state. There are conditions where that is not true, therefore I say 'should'.
In a take-off, the aircraft is rolling on its wheels and needs to rotate around the main wheels in order to increase angle of attack for liftoff. This means either to decrease tail lift (say, on a taildragger where the pilot has lifted the tail off the runway earlier in order to reduce drag) or to increase tail downforce. In order to pitch up the aircraft, the center of pressure needs to move forward of the main wheel location and the center of gravity, which is done by pulling on the stick. So what is needed is not an absolute tail downforce but a decrease in tail lift. This might well be a downforce, but could also be a lower positive tail lift. Most likely, it is a change from around zero to negative lift on the tail.
As soon as the correct pitch attitude is reached, the pitch rotation has to be stopped by pushing briefly on the stick. This shifts the center of pressure briefly back, behind the center of gravity. After that, the aircraft is in the correct attitude for its initial climb and the center of pressure is at the same lengthwise location as the center of gravity. If it isn't, the aircraft accelerates into some pitching motion which is not desired in straight flight.
Disclaimer: This all assumes no pitch moment contribution from either engines or drag. Any additional moment from other than lift forces adds to the momentum equilibrium and requires the pilot to shift the center of pressure a bit fore or aft of the center of gravity for straight flight.

2) When the aircraft increases its AoA, the CP moves forward (towards the leading edge). Does this mean it would go ahead of the CG or move closer to the CG.

When the angle of attack of an airfoil with positive camber is increased, its center of pressure moves forward.
In potential flow theory, lift can be calculated as the linear superposition of a contribution from camber and one from angle of attack. While the camber-related part of lift is constant, the angle-of-attack related part varies linearly with this parameter. The center of pressure of the camber part is somewhere at mid-chord (details depend on the camber line; with a Joukowski airfoil the center of pressure is precisely at mid chord). The center of pressure of the angle-of-attack dependent part is at the quarter chord (the center of the area below the chordwise Birnbaum distribution of lift). The important part is the self-similarity of Birnbaum distributions for different angles of attack: The center of pressure of the angle-of-attack dependent part is constant and at 25% of chord for 2D flow and wings of large aspect ratio. Since lift at zero angle of attack is solely from camber, the center of pressure is at around mid chord and moves forward towards the quarter chord point as angle of attack increases. But this would make an airplane with only a main wing using a positively cambered airfoil unstable in pitch.
Hence the addition of a tail surface with less loading than the main wing. Since it operates on a point of the lift curve slope that is lower than that of the wing, a change in angle of attack means a larger relative lift change on the tail which shifts the center of pressure of the whole aircraft back as angle of attack is increased. However, as this happens, the pilot will pull back on the stick, reducing some of the additional tail lift in order to keep the center of pressure close to the center of gravity.
In short: The center of pressure is always very close to the center of gravity unless the pilot commands some pitch acceleration.

Well, that's it then, we'll have to make graphs.  How about pitch torque, wing and tail, about CG with varying AOA.  Move CG back, replot, what happens?  Great to work on this, don't mind the heat.

Could you please explain what centre of pressure of the "whole aircraft" is? Because I know that the CP of "a wing" moves forward with increase in AoA.

@Johnson: The center of pressure is the point where all lift forces can be summed up. Do it for a wing alone and you have the CP of that wing. Do it for the whole airplane and you have the CP of the whole airplane. Easy as that.

Ok, you said "a change in angle of attack means a larger relative lift change on the tail which shifts the center of pressure of the whole aircraft back as angle of attack is increased". I also know that the CP of the WING moves FORWARD with increase in AoA.  WHY THIS DIFFERENCE? I just want to know why the CP of the wing moves forward whereas that of the whole aircraft moves rearward with an increase in AoA.

@Johnson: Key is lower lift on the tail. The AoA increase means more relative lift increase on the tail, since lift there was low or even negative before. Of course now the CP of the whole airplane shifts back – we have now more lift there.

1) When the aircraft is taking off, is the tail down force required to pitch up the aircraft high? Because the aircraft always has a natural tendency to pitch down.

For rotation, yes. Aft stick increases elevator/stabilator trailing edge up, which increases the downward force on the tail, thereby producing a positive pitching moment and increasing pitching angle/AOA.

2) When the aircraft increases its AoA, the CP moves forward (towards the leading edge). Does this mean it would go ahead of the CG or move closer to the CG.

No, as AOA increases from the trimmed flight condition, the CP of the whole airplane moves rearward assuming the pitch control is fixed. This is a requirement for pitch stability: as AOA increases, we would like the airplane to automatically pitch down (via aerodynamics without pilot compensation). This means that CP has to move aft relative to the CG to produce this negative torque.
I'm not sure how these two questions are related. Maybe if you can clarify a bit further, we can produce better answers.

"For rotation" see Space Shuttle.  By design, a tricycle landing gear lowers AOA to help plane "stick" once nose wheel is down.  Overdoing rotation can stall an aircraft.  "We would like the airplane to pitch down", well, sometimes it doesn't, if CG limit is abused, and/or if Hstab/elevator (or stabiliator) is not designed properly.

@JYZL if your model can incorporate tail area and coefficient of lift data to compute CP, it would very interesting to generate pitch stability vs AOA graphs based on these parameters.  These would go towards "drawing board" design considerations, and help set safe CG limits.

And hence we get to the issue with the MAX, where the whole a/c CP or Neutral Point was moving forward, or maybe more correctly, not sufficiently aft, as AOA went up, due to the lift being generated by the nacelles.

As far as the takeoff goes, the tail is doing its hardest work then, because its downforce must overcome the direct mechanical leveraging of the center of mass about the gear's runway contact point until the wings are supporting the weight, and it has to be able to do this at the most extreme case of being able to drag the tail on the ground at minimum takeoff speed. "Minimum Unstick Speed" (Vmu) testing, where the plane is flown off with the tail dragging on the ground, establishes this.
How hard the tail has to work depends on the gear's fore/aft location.  The worst case is on airplanes with tail mounted engines that have a more rearward C of G when not loaded with passengers than one with wing mounted engines.  The gear has to be far enough aft to keep it from tipping on its tail when unloaded (otherwise, a tail strut would have to be deployed whenever the airplane was unloaded - very inconvenient) and as a result the tail's job on rotation is harder than on the same airplane with wing mounted engines and gear that is not so far aft.  This is one of the significant downsides to rear mounted engines because more tail power, more area or more speed, than would otherwise be needed is required.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


text:
Is it cheaper to drop cargo than to land it?
Is it more fuel efficient to drop cargo onto a runway from the air en route to a final destination than to land and unload it using a more fuel efficient plane?

Interest only: An uncle used to drop humanitarian aid supplies in Africa from a Hercules, altitude as close to zero as terrain and nerve allowed. Somewhere under 50 feet typical.  Grain in sacks often split open. Add another sack outer - these occasionally split open. Add ANOTHER sack outer. Hooray. Triple bagged grain sacks NEVER split open. [[Not too too long before that he used to deliver stuff over Germany at night from a Lancaster, but after a while the recipients invited him down for about a 3 years break]].

That scenario only makes sense if your airplane stays at cruising altitude: although taxi and takeoff does use up fuel it's really the ascent to cruise that takes the most. You aren't really going to be able to drop cargo accurately from cruising altitude, so you'll have to descend pretty low, then you'll need to climb up again, and that would suck up lots of fuel and make it much less efficient a method of delivery.
Add to that the weight and cost of the parachute mechanisms as well as the massive protective packaging the cargo would need to survive the jolt (2-3 Gs when it hits the ground) and the whole thing becomes pretty uneconomical.
The military only air drops cargo when there's no other alternative - now you know why.

Precision high-altitude drops to within 50-75m using GPS-guided steerable parachutes are a thing..

@JörgWMittag From your source "achieving a high degree of accuracy (less than 100 yd (91 m)) requires the aircraft to fly at the lowest altitude possible, which can range from 400 ft (122 m) above ground level to as high as 1,500 ft (457 m)" That does not sound high-altitude to me.

@AEhere That's talking about normal airdrops. The next paragraph says JPADs can achieve the same or better accuracy from greater heights, allowing the aircraft to drop the load at a much higher, and usually safer, altitude.

"Protective packaging" : I am surprised nobody has mentioned Maxim 11 yet.

"Everything is air drop-able at least once", eh @MartinBonner?

The first airmail service (at least in the US) would deliver and pick up mail without landing by using hooks and nets. Similarly, train mail would also deliver without slowing down with the help of a hook. This saved time, and I wager, due to the very low cruising altitude  and slow speed of Inter-world-war era mono-planes, was fuel efficient.

Keep in mind those airplanes flew slowly @crasic.

@Rawling fair enough, I was confused by the lack of actual or claimed accuracy for the system. From one of the wiki sources: "Unlike the lighter JPADS 2K’s 150m accuracy, the 10,000 pound capacity JPADS 10K is accurate only to within 250 meters." with remarks about approx. 25kft ASL as the drop altitude. That article could use a revision for clarity and consistency.

Keep in mind that the cargo the military drops is ruggedized to begin with, and has lots of crushable padding.

@GdD ... and that they still suffer a significant percentage of losses when dropping more breakable things like vehicles (vs crates of food or ammo).  Crush pallets/etc work better on level ground than when one corner lands on a rock that's a few feet higher than the surrounding surface.

A surprising amount of air dropped military equipment self destructs and is not reusable.

Looking purely at operational cost of the aircraft, yes. You save time, burn less fuel, don't have to pay for the landing etc.
But dropping the cargo makes the cargo more expensive. You have to provide parachutes (and return them after use, inspect them etc). You have to combine cargo into parachute loads. You have to package the cargo for a hard landing, getting pulled over on its side by the parachute after landing etc.
You have to use an aircraft suited for airborne dropping (i.e. with a tail ramp). Commercial cargo aircraft usually don't have one, so you have to switch to more expensive military aircraft (Hercules, C-17).
And occasionally a parachute won't work and the cargo will dig a crater.
You can also go for low-altitude horizontal extraction, but that also has its cost, and entertaining failure modes.

Good summary, I'd add to this many cargoes can't handle the g forces from landing, even with chutes it's still a few Gs.

Note that the OP specified in the question that the plane doing the land-unload-takeoff is more fuel-efficient than the plane doing the drop. So, the question which of the two options im more fuel-efficient cannot be answered other than "it depends on how much more fuel-efficient the other plane is".

OF course you also save the cost of building a runway in the first place

"And occasionally a parachute won't work and the cargo will dig a crater." Even if it doesn't, the cargo is unlikely to survive it. Cargo not surviving is likely to drive-up the cost of transport.

@Mast: Those Humvees falling off their parachutes in the video you linked was due to sabotage (https://www.npr.org/sections/thetwo-way/2018/05/10/610099456/video-soldier-who-deliberately-destroyed-airdropped-humvees-found-guilty-dischar), not normal failure.  Yes cargo damage is likely, but craters aren't.  The link you chose doesn't support either argument.

@PeterCordes There was no crater in that link, that was the point. No crater, plenty damage.

@Mast: ok, but terminal-velocity impacts like that are much more unusual than that video of sabotage would lead you to expect.  The video hardly has the resolution to let us tell if there were literal craters or not; I expect there would be a very minor one if you got up close, given the puff of dirt.  Some of the very-low-altitude drops in the video Hobbes linked show a parachute that failed to open in time, but that's a compilation of fails, not multiple failures out of a few drops.  (And it's a specifically low-altitude drop that is maybe more risky than using enough parachutes higher.)

The main advantage of landing is that the plane can then carry another cargo on the return journey. Flying an empty plane back home is extremely inefficient and halves the range of the plane.
Air dropping might make sense for a large number of relatively small but urgent packages with lots of destinations along a route, but even then the plane would be mostly empty towards the end.
Dropping a load by parachute is fairly difficult, but loading a plane in the air is a real challenge!

Outside of any of the difficulties associated with dropping cargo out of a plane at altitude, the answer is still 'it depends'.
For long distance flights, a large part of the initial weight of the plane is due to the fuel load, not the cargo. This fuel weight imposes a penalty on both climb- and cruise performance. It may be beneficial to land halfway and refuel, so that on both legs of the journey, less fuel has to be carried. This is also why refuelling is typically done at every stop (unless poor availability or high fuel costs forces 'tankering' - landing with enough fuel left to do a return flight or the next leg as well).
The only use case for commercial cargo drops seems to be if you need to deliver cargo at a number of closely spaced airports (in which case the short hops would be fuel-inefficient). However, in that case you might as well use road or rail transport. The only remaining use case, which is unsurprisingly the only use case in reality, is to drop cargo if no other means of delivery are available - for example, conflict zones, disasters, etc.

Depends entirely on the constraints. So: "Sometimes" or  "maybe".
There are a few effects that make landing more fuel efficient:

On long trips refueling midway is fuel efficient, even if it involves landing.
Saving a second trip by loading new cargo midway is even more fuel efficient.
Having lower weight cargo due to absence of air drop packaging is fuel efficient.
Saving a trip due to tightly packed cargo is fuel efficient.

Related:

Dropping a parachute over a runway from high altitude can disrupt air traffic for a significant amount of time.
Dropping a parachute over a runway from low altitude means having to climb again, which is not fuel efficient.

There are many (contrived?) scenarios where none of these arguments come into play - in those scenarios air drop is indeed more fuel efficient. These scenarios would usually involve short distances, inherently air droppable cargo, runways that see very low amounts of traffic, and machines that will stay at relatively low altitude during most or all of the trip.

RE your next-to-last bullet, that is easily solved by delivering air-dropped cargo somewhere other than an airport.

@ThePhoton Absolutely. But I assumed that to be a requirement of the question.

I guess he did say "onto a runway", but there's no reason we couldn't build a runway someplace where there's no airport.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
What causes a helicopter to autorotate farther?
Which characteristics improve a helicopters ability to glide a farther distance in autorotation? Do these same characteristics reduce minimum decent speed in autorotation or is that affected differently? If so, how?

Surely this is not opinion-based; there must be real definable characteristics at play.

In general, regardless of the number of blades, the more blade inertia, relative to blade area, the better for autorotation safety because the inertia buys you more time to establish the autorotative glide before blade stall when power is removed, and more time to settle into a landing at the end of the glide.  The downside is more sluggish response to power application and maneuvering inputs on top of the added weight itself, so there are the usual tradeoffs.
The Robinson R22 started out with very low blade inertia for maneuverability (Robinson did not initially intend the R22 to be a trainer), but blade weight was increased later in production to make the aircraft more forgiving, to help with the blade-stall-following-power-loss accident rate.  In the earlier R22's you had under 2 seconds to lower collective pitch following a power loss before rotor RPM decayed enough to get blade stall, and if you weren't fast enough, that was it - you were trapped in a falling object (that's not as bad as it seems - if a car stops or swerves in front of you, you have a hell of a lot less than 2 seconds to react to avoid being killed, don't you).
In large helicopters or smaller machines with high inertia rotors like 2 blade Bell machines, you have oodles of time to establish the glide and settle after the flare.  A Huey can be lifted into a hover, held for a couple seconds, and settled on the ground just on rotor inertia alone.
You see a somewhat similar issue between regular airplanes and flying lawn chair ultralights.  When an engine quits on an ultralight, because the thing is big with lower mass, it slows down pretty fast and you have to aggressively shove the nose down right away to maintain flying speed compared to something like a Cessna 150. And a helicopter rotor is just an airplane going in a circle.

As a demonstration to the student, of rotor inertia, I've heard of Huey instructor pilots cutting power on the ground, then lifting into a hover with a 360 pedal turn and landing on inertia alone.

There are two more factors that contribute to good autorotation performance -- low disk loading and the installation of a tail wheel, bumper or skid to allow landing in the flare, and protection of the tail.


text:
A320 Avionics Compartment Access Door (Seeking Photo References)
We're software developers currently working on a 3D A320 for training and we're getting quite stuck finding any suitable references of the Aviation Compartment Access Door - specifically both it's exact location in relation to the Access Panel, as well as its operation (what needs to be pushed/pulled/twisted etc. and in what order).
Online we've only managed to find 2 or 3 blurry reference images that are on an A320, and due to Covid we're unable to arrange a site inspection with our usual hosts to capture the details in person (we usually combine photos and 3D scans). Given that our application is for training we want to ensure we replicate it as accurately as its real-world counterpart as possible.
Any reference images, videos and/or descriptions that anyone might be able to share would be really helpful.

Writing software to train students on something that you're not familiar with & haven't seen in person... not your fault, but still, doesn't exactly inspire confidence in the quality of the final product.

There are at least 5 access doors to the forward avionics compartment, you need to be more precise (which rack). This can help (p28) --> 811 and 812 are such doors. Agreeing with @RalphJ, and also that it's not your fault.

Ralph & @mins absolutely fair assessment - rest assured our subject-matter-expert stakeholders won't be letting anything through until the content is formally validated as accurate, right now we just need enough detail to scope the complexity of the project particularly around the 3D modelling and operation so we can estimate the cost, and while our experts are unable to access aircraft themselves we have to seek community help to get us by. Thank you for your feedback, we'll send your supplied link back to our stakeholders!

@mins Stakeholders confirmed it's access door 811 that we're looking for photo and/or video references on, thank you for that

Ok, sorry not being able to provide the answer, one last boost: This FAA re-publication states: "Open the access door 811, refer to AMM Task 52-41-00-010-002" referring to the task description from the aircraft maintenance manual. The overall view of the area can be found also in this Airbus firefighting training poster.


text:
What is the fuel burn of the APU on the CRJ900?
Looking for a reference from an FCOM, AFM or other manual for the fuel consumption per hour in pounds or kilos of the Honeywell RE 200 APU on the CRJ900.

It's surprisingly hard to come with that sort of data.  It's hard to come up with a fuel burn number because the fuel burn varies widely, because the loads vary widely, between electrical loads and bleed demand.  However, it's not too hard to come up with a theoretical maximum and estimate from that.
The best way to make an educated guess is to take the baseline HP rating of the Honeywell RE200 APU used in the CRJ7/900, around 325 hp, and work out the fuel burn at maximum power from the typical specific fuel consumption of turboshaft engines, which is somewhere around .5 to .6 lbs/hp/hr.  Say to be conservative, we'll use .6 lbs/hp/hr.
So wide open, the APU will be burning .6 x 325, or just under 200 lbs/hr.  It might get close to that if you are running all of the electrics off the APU gen and both packs.
Normally however, the demands are going to maybe 1/3 to 2/3rds of that.  If it's idle, it might be burning 30-50, and with bleed loads due to running the AC packs, maybe 100-150.
So I think you could use 100-125 lb/hr as a ballpark value when you want to allow for fuel used by the APU while on the ground and providing air conditioning and powering the electrical system. Or if you just want to assume the worst case and go by that, for an hour of sitting on the ground with the APU running everything, you can safely assume it's going to use not more than 200 lb of fuel.

I think it's an expression of bleed flow incorporating volume and pressure. Can't remember for sure now.  It's been a while.

Yeah if you learn the SFC's of different engines, you can work out the burn for pretty much any power setting if you know the HP being made.  .5-.6 for turboshaft/turboprops, about .45 for carbureted piston, maybe low .4s for injected piston, high .3s for modern cars, low .3s for diesels.  The turbo compound Wrights were extremely fuel efficient, actually down in the car range. I seem to remember it was something like .38.  Each engine had what amounted to two Lyc O-320s helping it out for free (each exhaust power recovery turbine made about 150 hp x 2).


text:
What organisation owns intersection names?
I understand that five letter intersection codes (such as WARPI, PAPPI, KUBBS, ROSLY, ZALPO, ...) are unique in the world.
However, their names don't comprise a national prefix (as aircraft tail number do, or airport codes do), which would allow to delegate name bookkeeping to the individual countries's aviation authorities by prefix.
Therefore, a single, international organization has to somehow own and disambiguate all the intersection names. I would expect the ICAO to be that organization, but I haven't been able to find any resource mentioning that.
Help?

Intersection codes are not actually unique in the world, unfortunately. There is some overlap between FIRs, but not much. Usually any duplicates are quite far away from each other, but long distance flights mean that they do occasionally show up within a single flight plan.

Closely related

is "intersection code" just a synonym for "waypoint name", or a subset?

The allocation of waypoint names is actually handled by each country's individual aviation authority. This means that there are actually duplicates in different countries or regions. The ICAO has made at least two attempts to remove the duplicates and make the names globally unique, one in 2010 and another in 2018. Despite these efforts, there are still over 1000 duplicate waypoints in the ICARD database.

As already said in HiddenWindshield's answer, the five letter intersection codes do not have to be unique worldwide. I thought it might be interesting to see how many times these codes are actually being re-used.
Using my current navigation database (AIRAC 2006), I made a search for how many times each code is used. The following histogram shows how many times codes appear worldwide (note the logarithmic y-axis):

Out of the 124,215 codes, there are 119,973 unique ones (only used once) and there are in total 4,242 ones that are used more than once. The highest number of uses has the code ALPHA with 9 total uses worldwide.
Usually, intersections with the same code are far away from one another to avoid confusion. There are however some quite close re-uses. I searched through my database to find the closest two intersections using the same code and came up with two SIERAs used in Belgium, which are only 18.5 NM away from one another:

What other context is provided with a waypoint that would allow someone to  differentiate these two SIERAs?

@zymhan Neither are part of an airway. My guess is that both of these belong to some instrument procedure (SID/STAR), but for two different airports. Unfortunately, my navigation database does not say to which airport these belong, so this is just a guess...

Having had a look at them, they are VFR waypoints, unrelated to any specific approach procedure

Omg having two VFR waypoints with the same name that close to each other is just downright stupid.

@Jpe61 almost makes me wonder if its an error in the database or something? or if there was conflicting definitions published at one point that somehow turned into the two entries?

@Jpe61 Why should it be? It is not stupid at all. ALL southern reporting point point on EVERY airport around here is SIERRA. ALL northern one are NOVEMBER, ALL eastern ones are ECHO and ALL western ones are WHISKEY. I do not see anything stupid about that, you know where to fly, they are specific to the airport in which CTR or ATZ you are inside. The only weird think is how did the VFR reporting points appear in that database.

@VladimirF imagine a situation in the case above where two planes are flying about in the middle of the two Sieras, headings of 045 and 225, and have not spotted  each other. One gives posrep "Xyz is 9 miles SE of siera heading 045". Its noon, so sun will be at about 225. See where I'm getting at? Both might be adhering to proper VFR ENR alt, but then again, migh not. Or might be changing alt.

This might be a small risk, I admit to that, but one the would be so easy to mitigate.

@Jpe61 But such points are not enroutte points, they are reporting points for entering or leaving that specific CTR or ATZ. If enroute, you always say which airport you are flying to in the first place. Only then  you care which point you will use to enter the zone.

Thank you for your answer and your research!

authors: Vladimir F Героям слава


text:
In Antonov An-225, why there are radioactive / nuclear signs?
Looking at some An-225 images, i see some radioactive signs near the nose radome. Why they are there? I'm sure it doesn't have a nuclear reactor on board or any nuclear medical equipment. The only thing that comes to mind is nuclear density gauges or something related to the radar. Does other planes also use radioactive materials for the same purpose? I've never see, read or heard of any plane using radioactive materials except for propulsion.

Images source:
https://gelio.livejournal.com/193025.html
Find this link on this answer:
Does the Antonov An-225 have an Auxiliary Power Unit (APU)?
https://en.wikipedia.org/wiki/Nuclear_density_gauge

You probably should highlight the symbols - I had to copy the image and zoom in to determine where the symbols are located

"Radiation" is a broad term and does not always imply radio active isotope material. High power radar units can have adverse effects on the human body.

The power that radar systems emit varies from a few milliwatts (police
  traffic control radar) to many kilowatts (large space tracking
  radars). However, a number of factors significantly reduce human
  exposure to RF generated by radar systems, often by a factor of at
  least 100:

Radar systems send electromagnetic waves in pulses and not continuously. This makes the average power emitted much lower than the
  peak pulse power.
Radars are directional and the RF energy they generate is contained in beams that are very narrow and resemble the beam of a spotlight. RF
  levels away from the main beam fall off rapidly. In most cases, these
  levels are thousands of times lower than in the main beam.
Many radars have antennas which are continuously rotating or varying their elevation by a nodding motion, thus constantly changing the
  direction of the beam.
Areas, where dangerous human exposure may occur are normally inaccessible to unauthorized personnel.

The warnings are likely due to the emissions of the radar units in the dome.

Radar is non-ionising radiation which has its own hazard symbol. The trefoil symbol is specifically for ionising radiation only.

@Sanchises, well, the fact is, this symbol is commonly used for strong microwave rarar radiation. At least in Russia (or Ukraine for that matter). For example, on Su-27.

..which is unfortunate as the hazard profile is different:(


text:
Why does the Winds Aloft ‘For Use Time’ start before the ‘Valid Time’?
Why is it that a winds aloft forecast normally has a "valid time" that comes in the middle of the "for use" time range? Why don't they just state the valid time as the beginning of the for use time period?

Welcome to aviation.SE! To make your question as clear as possible, it would be helpful to add a specific example.

Wind and temperature aloft forecasts (FB) are computer-prepared and issued by the National Centers for Environmental Prediction (NCEP) at Suitland, Maryland. The forecasts are valid 6, 12, and 24 hours after the observation date/times of 0000Z, 0600Z, 1200Z, and 1800Z based on National Weather Service Instruction 10-812, Aviation Wind and Temperature Aloft Forecasts.
Source: FAA 7110.10

In essence, it's a subtle way of telling you it's a best guess based on observations and computer models, and it covers a time period where they think the model's conclusion will be closest to the real thing. Like medicine, weather forecasts are not an exact science.

I think my English is pretty clear.

Well, like, now it is

Second, slower readings always seem to help, don't they...

I concur. The original wording was, however, not as clear as the edited one.

The wording of the last paragraph never changed. Anybody can see that. I consider this subject closed.

Anyone can see that the wording of the last paragraph has changed. Please see for yourself. I made the edit on Jul 24 at 8:28. If you wish, I can do a rollback.

Oh now I see what you did. And you think because you added "Just " to the beginning of that sentence, that justifies your bizarre comment? Are you kidding me? LOL! I am DONE with this dumb thread.

Well meanwhile my bizarre comment has been deleted, for one reason or another, so case closed. My comment was made in benevolent manner, but it obviously was readable as offensive, as is the case with any internet content these days.


text:
Station Passage for an NDB
I read somewhere that the first station passage for an NDB holding pattern is when the bearing pointer passes the 90 degree index. Then the document went on to say that for subsequent crossing of the holding fix, station passage was when the bearing pointer passed the 45 degree index. Why? Is this just a technique, if not, what is the reason?
I read this in the appendix to an Air Force manual.

References are always good ...

If you're decently aligned overhead when crossing the beacon, it flips around fairly quickly anyway. It's probably a way to anticipate and lead the turn a bit to fly a tighter pattern, but I don't think it makes much difference and you have plenty of protected airspace around you.

Do you know where your read this?

I had no idea people were still flying NDB holding patterns. Was the music that good? :)


text:
General advice on flight simulator hardware
I am new to flying and have only had a couple of lessons in a Cesna 152 but want to get some practice on a simulator as I'm quite old and don't learn quickly compared to youngsters. My instructor wasn't too forthcoming but mentioned that the Microsoft flight simulator was the best software if I wanted to get some practice of that type. I believe I would also need a flight yoke system for a Cesna 152 however am concerned that I don’t waste my money on wrong kit. I believe I would need in addition to the software  a yoke , instrument panel and rudder controls.  I appreciate that its no substitute for practical flying hours but with current lock down under COVID being strictly enforced where I am there is no chance of getting into a plane in the next few months. Please can you   advise suitable products with any links. I have also seen some ads for VR headgear would that also help me?
Thanks

Welcome to the site @oldboy. I was an avid MS Flight Simulator fan before I did the real thing, and my opinion is it doesn't teach the right sort of lessons. Flying an airplane is easy, the trick is learning how to aviate, navigate and communicate at the same time, and PC simulators don't really help with that. Fast isn't always good, so go at the pace that is right for you, and enjoy the experience!

I learn to fly at 19yrs in1975 but didn't get a jet type rating until my mid 50s, in an extremely intense type course. My observation was, the old fart learns the physical easily, but struggles with memorizing data.The youngster is the opposite (clumsy teenagers).At this stage, concentrate your time on memorizing data, procedures etc and drill them to death.Learn the physical skills first in the plane.Use the computer sim (FS is great for this) to hone a procedural skill you've learned to do correctly. The biggest downside to home sims is the ability to teach yourself/reinforce the wrong thing


text:
What are the main visual differences between Spitfires and Hurricanes?
I've heard that Supermarine Spitfires and Hawker Hurricanes were both great fighters, but what are their distinguishing features?

Albeit having photos in the title, the linked duplicate should answer your question.

What can we tell you that isn't apparent in the pictures?

I'm not sure which plane is which.

The Hurricane has a humpy back and a cockpit like a greenhouse; the Spitfire doesn't have these things. I have known that since I was aged about 8.

The top one is a Hurricane, the one on the bottom is a Spitfire.  Study them.  A picture is worth a thousand words, and no amount of words will help if you can't distinguish them visually yourself.


text:
Were cabin lights really consuming that much power back in 2006?
Even though it is nine years since then, I can still clearly recall my return flight from London Luton to Katowice (Poland), that I took on July 31, 2006 evening. There were a huge, strong storm front coming to Poland (ten days of extremely high warmth followed by ten days of an unusually high raining and really strong stroms, that started on August 1, 2006 in Poland), that we hit somewhere over Germany (hit or flown somewhere around / near it).
I was then and I am now a layman in aviation, so my description and terms used my not be correct, however I recall, that it was really a bumpy ride. Plane was falling down (loosing 100 ft or so) and trying to  go back to previous altitude etc.
At some point, one of a pilots informed everyone on board, that they'll be dimming all the cabin lights, because "they need more power to the engines to go through this strom". And soon after that, they really did that and for about 10-20 minutes we were flying in a very limited cabin lightning.
Is this true, what we have heard nine years ago? Were cabin lights really consuming that much power back in 2006? Or was that just a strange way pilots wanted us to get a little bit more scared?
I was flying with Wizzair, so I assume, that it was A320. There is a similar answer on similar matter, but it says about LED-based cabin lights system and I can hardly believe, they were introduced to "cheap" Wizzair's A320s back in 2006.
But, even assuming, that our plane was fitted with a "typical" lights, much more energy consuming that LEDs, it is really hard for me to believe, that cutting on cabin lights could bring any noticeable power to airplane's engines. Correct me, if I'm wrong.

Just as an aside, the plane almost certainly wasn't dropping 100ft per time. Even in extreme turbulence (the kind that knocks trolleys over, breaks cabin crew arms from throwing them around, throws luggage out of the overhead racks) the plane is only likely to lose 10-20ft of altitude. It just feels like much more.

Thunderstorms normally mean icing conditions, which necessitates anti-ice, both through bleed air and electrical systems.
I can see this going a few ways:

Pilot is (for instance) at high altitude and really does need the additional bit of power to cross above the thunderstorm.
Pilot has flown aircraft type where this is a legitimate problem and figures 'why not?' for safety sake.
Could be something about motion sickness in the storm, since closing your eyes can be an effective countermeasure. Perhaps dimming the lights goes along the same lines.

Since it happened in mid-flight, then I assume, that it actually was a cruising altitude and option (a) on your list would fit best.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Is it possible to divert a plane to a distant airport?
Some years ago I have spotted that an Eurolot flight from Amsterdam to Gdansk, diverted close to final approach to a distant airport on the other side of Poland:

Is this another example of Flightradar24 bug and it is more than possible, that this particular flight actually landed in desired destination airport? Or are there any business or operational rules or some special situation, that would judge diverting a plane to a distant airport, while having at least 5-6 other airports closer "on the track"?
For me -- layman -- the answer is: No, there are no such reasons and airplane is always diverted to the nearest airport, that is able to accept it (taking plane type, weather conditions etc. into account). But, I'd like to get some expert confirmation, if there are no exceptions from this rule of thumb?
EDIT: In my opinion, we're dealing with a quite different situation here than in previous question (and that's why I didn't merged both questions into one). Mainly, because:

flight path IMHO is clearly suggesting a diversion, not an error in Flightradar24 and
plane's vertical speed is suggesting, that plane is actually landing in the moment, this screenshot was captured, and since I was living in Katowice for over 30 years now, I'm pretty sure, that there was not direct flight on AMS->KTW route, neither by Eurlot nor by any other airline and neither at the moment of capturing this screenshot nor right now.

So there actually was no other flight between Amsterdam and Katowice that Flightradar24 could mistakenly taken as this one.

I think you could have just edited your other question rather than posting a new one.

I'm voting to close this question as off-topic because it seems to be asking about a software bug in a 3rd party service.

@fooot Well, I'm assuming, that these are two different questions focused on the same topic. Plus: I'd have to completely reedit original question, adding all the knowledge that was expressed in comments, and that would make these comments invalid and the edit itself beyond certain border. But, I might be wrong again.

@Simon If nearest airport is usually picked only in emergencies, then this makes the case even more interesting. Do you have any source of information on can craft some answers to say something more about these factors and rules, that are taken into consideration in non-emergency?

There are lots of factors in deciding to where to divert and nearest airport usually only applies in emergencies but not that far. Given your last question, I would say that Flightradar24 is at best suspect.

I would close this question and ask a new one which is very specific, for example "what factors are used in deciding where to divert".

Weather, governmental restrictions, wanting to stay out of contested airspace, military operations, political tensions, etc are all good reasons for a flight to fly longer than expected paths. The path you have in your image is not a diversion (which involves landing at an airport other than your intended destination), its more like a long-route.

@Simon Voteups on both questions seems to be suggesting, that these aren't that bad questions, but I consider your suggestion, of course.

@RonBeyer Vertical speed of -1500+ fpm seems to be suggesting that this particular plane is actually landing in Katowice, instead of Gdansk. How can you call a "long-route" instead of "diversion" for plane landing on a opposite side of the country? I'm asking, because this seems to be beyond my imagination.

Again I wouldn't take FR24 data as gospel (especially considering your last question), I'm talking in general. If you are interested in this particular flight, have you verified the flight was actually diverted with the operator or less buggy sites?

@RonBeyer Now, I haven't and since we're talking about screenshot captured about 2-3 years ago, there is no way I can do this right know. But, consider arguments expressed in my edited question.

Your edit does not help.  So there actually was no other flight between Amsterdam and Katowice that Flightradar24 could mistakenly taken as this one.  This is flawed.  You assume that the bug is that it confuses 2 flights.  How about "Last time we know, the aircraft was here.  Now it's over there.  I will draw a straight line between those 2 points".  If "here" or "over there" are wrong, then the line is also wrong.  I think you should ignore Flightradar24 and find alternative sources.

I've read the arguments and I still can't say that you can take any data as gospel for FR24. Perhaps FR24 thinks its near Krakow but really its closer to Gdansk. Maybe the lower part of the flight segment is the actual error and the aircraft is descending into Gdansk...

The diversion airport is selected by the captain¹.
If the aircraft needs to divert for some urgent reason like engine failure, smoke/suspected fire/fire, medical emergency and similar, the captain will select the airport so that they can land as soon as possible. However from cruise altitude even expedient descent still takes about 15–30 minutes and the plane can cover 50–100 nmi, so they still have some choice in most places, especially densely populated areas like Europe.
But there are many less urgent reasons that warrant diversion. The most common is of course that the intended destination is closed due to weather, accident or other problem. And then there are problems like pressurization failure that require descent to lower altitude where the fuel consumption is higher, so the plane no longer has enough fuel to reach the original destination, but still has fuel to fly considerable distance.
Sometimes the plane can even reach the intended destination just fine, but some fault occurs that would be hard to fix there, so the plane returns or diverts somewhere it will be easier to fix.
In these cases, the captain calls the airline dispatching (over radio, HF radio or satellite phone) and discusses with them where they should divert to make least disruption to the overall airline operations considering things like ability to fix the diverting plane, availability of replacement plane or alternate connections for the passengers, availability of replacement crew to fly the replacement plane or this plane after it is fixed, availability of airline representatives to take care of the passengers and many other things.
So something happened and for some operational reason it was easier for the airline if they had the plane in Krakow than if they had it in Gdansk (or, if it was not possible to have it in Gdansk, better to have it in Krakow than, say, Warsaw, which was still closer). For example I remember reading about incident where wind shield cracked on a plane already on approach to their destination, Klagenfurt, and they returned to Vienna and sent the passengers by bus. Because it was apparently easier (and cheaper) for the airline than fixing the airplane in Klagenfurt without suitable hangar (with cracked winshield the plane may complete the flight, but not take off again).

¹ Except really special circumstances like violation of foreign airspace and arrest by interceptors, nobody from outside can divert the plane. The pilots do.

I won't reply to the "is it possible the flight was diverted this far" bit, as other have given good reasons for this.
However, even though we're missing quite a bit of data, it seems quite obvious that this specific flight was never diverted: the AMS-GDN flight got out of range of FR24 on approach to GDN, and somehow FR24 took the following flight (from GDN to somewhere else, probably Krakow) as the continuation of this flight. Full data history would probably show a big gap in the data between the two sharp "turns".
This is consistent with:

the times shown (ETA 9:09 PM CET, actual time 21:47 UTC which is 10:47 PM CET, well into the next flight),
the actual paths which are clearly aligned with GDN (both inbound and outbound),
the fact that the "turns" are way too sharp,
recent flight history for the aircraft (which flies GDN-KRK on a very regular basis)
the absence of any other aircraft on the map in the GDN area

Remember this is a Dash 8, which is not equipped with ADS-B, but a simpler Mode-S transponder, which requires multilateration (MLAT) and hence to be visible from at least 4 stations to show up on the FR24 map, and provides less data.

Great analysis and "investigation" on FR24 stuff and possible errors. Thank you. Pity, that I can only +1, but I can't accept your answer as it does not answer question directly. Anyway, great contribution! Thank you.

Is it possible to divert a plane to a distant airport?

I was on a flight that was diverted from Heathrow in the south of England to Prestwick in Scotland. It seemed like quite a long distance to me at the time.
There are actually plenty of airports closer to Heathrow than Prestwick.
This was due to major storms sweeping through the British Isles.
The plane was initially diverted to Manchester but that airport was closed before we got there. Prestwick was pretty bad but I think the pilot was probably running out of choices within fuel range by that time.

There are lots of factors playing into a pilot's decision as to which airfield to divert to.  Typically this will include:

Where that airline has a ground team e.g. a Easyjet flight inbound to Gatwick is unlikely to divert to Heathrow because it won't have any staff on the ground to deal with passengers, and it costs a hell of a lot to hire someone else's team!
What are the landing conditions at the diversion airfield e.g. if there is low visibility and fog at Charles De Gaulle, then the same weather might be present at Orly
The length of the runway - most passenger jets (say B737 and above) are going to be too large/heavy to be able to land at London City, so they'll choose to divert elsewhere
And, of course, how much fuel is left on the aircraft!  Pilots will want to have enough fuel to be able to safely abort one landing, circle the airfield and try again - as an absolute bare minimum.

As for fuel minima - it varies a bit from country to country and airline to airline, but a general rule of thumb is that the flight should have enough fuel to hold in a stack for a reasonable time (20-30 minutes at Heathrow), attempt a landing, and divert to their declared alternate.  So, if you're going to make the decision to divert early, then you could feasibly travel a good extra distance in pursuit of one of the items listed above.

Well I'd say, that this is one of the best answers, I ever found, made by person, who has just joined the community. Thank you very much for your contribution and congratulations on a great start.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Relationship between wing aspect ratio and speed
For some reason, I cannot find a relatively straightforward source online which discusses the relationship of wing aspect ratio and how it affects speeds of an aircraft.
Specifically, is there a decrease in efficiency to fly at a faster cruise speed as the aspect ratio of the aircraft's wing increases? Could an aircraft with a high aspect ratio - similar to those of gliders - travel at the same cruise speed as a jet?
Thanks in advance!

Did you search for aspect ratio as suggests by the help center before asking

this question Relation between drag and aspect ratio is highly related if not a dupe

Are you looking for an explanation or just a link to an explanation?

Yes - I read those other answers and searched before submitting. They don't specifically answer what I'm asking. I'm happy with either an explanation or a reference to one.

You should highlight in your question why they don't address your problem as they are really similar to your one.

It's really the other way around, speed of the aircraft affects aspect ratio.
Hawks fold their wings to dive at high speeds, and have them straight out for lower speeds.
At high speeds the main concern is drag.  The less drag, the faster you can go.  At lower speeds, the main concern is lift.  Here a higher aspect wing is more efficient.

Why not use a smaller high aspect wing at higher speeds, and just vary the sweep?

This is done, but along with higher speed comes greater aerodynamic forces.  This is one reason why modern fighters feature low aspect wings and deltas.  These are simply much more able to withstand higher G forces.
The variable sweep wing concept was developed in the 1950s and 1960s, but generally carries a weight penalty.  Variable camber is widely seen in airliners today.
Some military aircraft, such as the B-1 bomber, use variable sweep to expand their useful
flight envelope, giving them the ability to "get low and fast".
Cruise missiles, optimized for one speed only with little abrupt maneuvering, can be found with very simple high aspect swept wings, which offer an improvement in drag over a lower aspect wing, thereby increasing fuel efficiency and extending range
There is no direct relationship with speed and aspect ratio, indeed, high subsonic aircraft such as airliners, that strive for maximum efficiency, are seen with increasingly higher aspect ratios in recent years.
Structural strength is the main limitation which continues to challenge engineers today.

Hi Robert - thanks for your response. You say that "there is no direct relationship with speed and aspect ratio, indeed, high subsonic aircraft such as airliners, that strive for maximum efficiency, are seen with increasingly higher aspect ratios in recent years." So if you were to theoretically double the aspect ratio of, say, a 737, and maintained the same cruise speed, you would only experience an increase in fuel efficiency (ignoring other effects such as a decrease in maneuverability)?

Well, keeping the area the same, but reducing the aspect ratio would make a shorter, wider wing.  much more drag from: higher angle of attack required for same lift and more drag from the trailing edge, but much stronger, able to withstand higher G forces.  This is why the F-35 has its wing and the 737 has the higher aspect.  Look at sailplanes!  That is what you want as much as possible.  The ones with jets are baby airliners without sweep, slats, flaps, and multiengines that develop later in life.

You only lose efficiency when you have more wing than you need for a given weight, angle of attack, velocity, and air density as seen in the Lift Equation, which is why area is also included.


text:
Why do the two different "ground effect"s used by aircraft and automobiles do opposite things in almost the same conditions?
I found How come the ground effect has such a different outcome for wings and cars? and:
I am not allowed to comment as a new user because of some weird rule and I do not know enough to answer the question as I searched the web to find the answer to this.
Everyone is explaining that the two types of "ground effects" have the same name but are two entirely different phenomenons, but no one seems to have answered the question properly, at least that I can understand. It is all well and good saying they are different effects for different purposes but that does not explain why the two opposite effects occur in such similar conditions. I was originally searching for the answer to this question strictly in the context of car design - why the car-context ground-effect sucks the car down using the venturi effect yet having a full teardrop shaped car is meant to be impractical for the reason of creating a lifting air cushion underneath, though someone may think that the curve towards the ground would act as a venturi and suck the car down. The question is: "why do the opposite effects happen in such similar conditions". Venturi effect or air cushion? What decides which occurs?
I think aeroalias' answer sort of explained it but not in a clear and direct way; venturi effect occurs until the venturi is so extreme that the flow is "choked" and the venturi effect ceases to operate and you just have an air cushion? Is that the answer?
edit: This might make it clearer as to what I am asking though it is mainly a rephrasing of what I have already asked:
Why isn't an air cushion formed underneath a car (like with the aircraft) when the underside is curved towards the ground? Does the venturi effect occur when the curve is shallow but an air cushion form when it is steeper and flow is "choked"? I think I understand the basic theory of the car ground effect but what causes the aircraft ground effect and what conditions determine whether upward or downward force is produced?

"Everyone is explaining that the two types of "ground effects" have the same name but are two entirely different phenomenons" My answer argues that they are the same phenomenon with different outcomes. I added a small paragraph which should make the only difference between the two more obvious, although Peter Kampfs answer there gives a more accurate explanation.

@Sanchises, thanks! Your added paragraph really helped me understand the similarity

@Sanchises Sorry. I think your answer was arguing differently toa  lot of the others. So your answer is basically saying that having an enclosed area over the ground prevents air from either being replaced or escaping when it is sucked or pushed in? So in a sucker car like a chaparral 2J you can keep low pressure underneath but in a hovercraft you can keep high pressure underneath to keep it floating? I think Inunderstand that though I also think that is different to the commonly accepted emaning of "ground effect" for both aviation and cars which don't involved sealed areas or active suction.

You say "sealed" but neither case is actually sealed. The ground effect does increase very rapidly with smaller gap, so I used extreme examples to give an intuitive feel for the underlying physics. In the end, it's all about creating a barrier so that you need less downward airflow (=kinetic energy 'lost' to the downwash)  to generate the same lift. For huge wings, just the ground is more than enough; for cars, a smaller gap is required.

venturi effect occurs until the venturi is so extreme that the flow is "choked" and the venturi effect ceases to operate and you just have an air cushion? Is that the answer?

No. Neither answer to your linked question talks about venturi effect at all!
In the aircraft case the wing is still far enough above the ground there there is no significant venturi effect at all. The pressure field around the wing is still similar as in free flight, but because the air can't move down behind the wing, the effective angle of attack is decreased, which reduces the induced drag. It does not even increase the lift all that much, reduction of drag is the most significant effect.
In the car case the bottom of the car is much closer to the ground, but the venturi effect is still not the major part. The underside of the car acts as an inverted wing, which creates upward lift. The ground again prevents the, in this case, upwash, this time by preventing other air to fill in and this again reduces the induced drag. The point is again not creating more force, the point is creating the force with less drag, so the car can go faster with the same engine (most racing classes are limited by engine power or cylinder volume).
Also note that venturi effect would be always downward, so if it was true that venturi effect increases until it becomes “choked”, it would pull the aircraft (which has the wings higher, so definitely no choking) down and possibly (depending whether it would be choked under the car) push the car up, the opposite what is observed.

Hmmm... how is it then that it is often stated that ground effect for race car X is Y kg? Yep, guess it should be N in the first place, but anyway, it is often measured in hundreds of kilograms.

Thank you for anwering! I think I need to read up on aerodynamics a bit more to understand most of what you mean.

@Jpe61, I strongly suspect that is just sloppy wording calling the downward force ‘ground effect’ though it actually is just a downward lift and the ground just allows generating it with much less drag.

Yea, could be. After all, we are talking about an industry, that has named downward lift generating devices "spoilers"

@JanHudec Flow choking is a problem in all ducted airflows, and that includes both Venturi ducts and the undersides of cars. If it happens in a turbojet intake the engine "surges". If it happens in the cooling duct for an engine or its radiator, the engine overheats. If it happens under a car, the steering suddenly gets awfully light!

It is true that an aerofoil and a fast car both have streamlined and cambered profiles.
A wing in flight generates a high-pressure wave beneath it, which helps support the plane. This wave travels down to the ground and reflects off it. Normally the reflection trails well behind the plane, but very low down it can impact the wing and boost lift. This is ground effect.
When streamlined cars first attained high speeds, the effect was similar to that of a wing; a high pressure wave was created beneath it and reflected back off the road, the steering lightened considerably and the tyres' grip on the road loosened drastically. Ultimately, multiple reflections between ground and chassis could cause such a massive build up or wall of pressure that the flow was choked and drag rose steeply.
Early attempts to counter these undesirable side-effects included upside-down aerofoils at nose and tail. But bolting on fragile palliatives was never going to be a good solution.
Car designers turned to the wind tunnel and aerodynamics text book and there they discovered the Venturi effect. By designing the underside as a Venturi tube and avoiding flow choking, the whole vehicle became the upside-down wing.
In this respect there is really no difference between the upper surface of a wing and the wall of a Venturi tube, in fact it can sometimes be helpful to think of a wing as half a Venturi, or vice versa. Both generate the same horizontal flow acceleration and orthogonal suction via the Bernoulli effect. The trick with fast cars is to make the underside work harder than the top side and to profile the Venturi carefully to avoid the sharp decreases in area which cause flow choking.
The only problem then left was to harden the suspension so it did not bottom out at top speed.

So what happens if I have a flat plate at an angle of attack as it approaches the ground?
Will it 'support the plane' and push it up or 'act as a venturi' and suck it down?

Would be an interesting experiment. My guess is that at low AoA the lift would reduce due to suction but at high AoA the flow would choke and lift increase. But I could be wrong. It's what wind tunnels are for.

Wind tunnels don't explain why something happens :)

@ROIMaison You didn't ask why, you asked what. That is indeed what wind tunnels are for. Can you please stick to comments on the main answer.

I am allowed to comment now apparently. Thank you. I feel this is the answer that best answers the question. I think I need to learn a bit more to understand what Jan Hudec is talking about. So it is a case of venturi effect then after all, but only when the angle of attack is shallow enough? I also don't quite understand how a wing is like a venturi? I thought a wing is basic device that creates pressure underneath by forcing air under as it goes forward (if the front is higher than the back) or creates pressure above and therefore downforce by forcing the air over (when the front is lower)?

@ElliottSavva An efficient airfoil creates both low pressure above and high pressure below. Both the upper surface of a wing and a Venturi duct restrict the path of the air so it must accelerate to conserve mass flow rate and, by Bernoulli's principle, this causes a drop in pressure. Flat plates are a distraction, pay no attention. If you need diagrams, ask a new question so there is proper space to answer. (If you like the main answer, there should be a grey tick you can click to show it)

@GuyInchbald Ah, I did not correctly understand how a wing worked before evidently. So they passively accelerate the air on top more than underneath? I was watching a film the other day and someone was talking about wings and bernoulli's principle in it and said something to do with the upper side having more surface area than the bottom. Is that anything to do with it? I suppose that means there is more deviation from a flat line on top than on the bottom and the air has to move faster, presuming the same mass of air goes over the top as underneath rather than more?

@ElliottSavva The Wikipedia article on lift is worth checking out. It is a bit turgid and badly-structured in places, but it is fundamentally correct. https://en.wikipedia.org/wiki/Lift_(force)

@GuyInchbald Thank you. I will check that out.

the wing on a plane is designed to generate lift while flying in the open air. It happens to generate less drag when flying ~ten feet off the ground, because a "bubble" of air gets squeezed between the bottom of the wing and the surface of the ground and this helps support the wing. this is called "ground effect" for airplanes.
you want a fast car to stay stuck to the ground and NOT turn into an airplane, and for this reason the car's body is designed to work like an airplane wing upside down while always "flying" just a couple of inches off the ground, so it creates downforce instead of lift. To generate downforce while almost touching the ground requires the use of aerodynamic features that don't look much like wings, and the fluid flow properties they exploit are known as "ground effect" for cars.

But why isn't an air cushion formed underneath a car (like with the aircraft) when the underside is curved towards the ground? Does the venturi effect occur when the curve is shallow but an air cushion form when it is steeper? I think I understand the basic theory of the car ground effect but what causes the aircraft ground effect and what conditions determine whether upward or downward force is produced?

@ElliottSavva, the underside of a car is not curved towards the ground, it is curved slightly away from it.

@PeterKämpf, what I meant was exactly what you said, sorry for my poor wording, will delete the comment.

@JanHudec That's what I always assumed, as that would mean more volume and reduced pressure, but according to the venturi effect/bernoulli's principle the way I understand it, that would increase the pressure on the underside of the car, as the energy pushing the air along would be transferred to the internal energy of the gas (in order to slow the gas down as the wdth of the "tube" is increased) therefore increasing the pressure and temperature? What am I missing? I hear lots of things about high performance cars like Mclaren F1s and Jaguar XJ220s being shaped to accelerate air underneath.

@ElliottSavva, less volume => higher speed => lower pressure (as internal energy due to pressure is converted to kinetic energy). This is only relevant if the surfaces are very close together though. The other part of the effect is forcing the air to curve upward – just like wings make air curve downward – which reduces the pressure by conservation of momentum (it takes upward force to make the air change direction). This is relevant with any distance between the surfaces, or even no second surface, just having the other surface close reduces the drag from it.

@JanHudec Alright, so don't you have to curve towards the ground to reduce the volume? Thank you for the explantion about the upward movement too.


text:
What is this jet airliner flying over my house?
I took a picture of this jet flying over my house:

It looks like a 737. Took place on July 14, 2020 at 4:00 PM in Long Beach, California.

You should add the date, time and location. It's much easier to reference that with one of the tracking websites out there (eg fr24 or flightaware) than to try and identify an airliner from a few pixels.

Can't see exposed tires in the gear wells - definitely not a 737

The position of the sun's reflection on the fuselage nose shows that it is positioned very low – a clear indication of an Embraer type. The lower wing sweep and the long tailcone also indicate as much and are a clear indication against a larger twin like the Boeing 737 or the A320.
This leaves the E 179, 175, 190 or 195 as possible candidates. The 190/195 have a stretched fuselage and to me fit the one in the picture better.
So I guess this is an Embraer 190 or 195. Both are very similar, so I am not able to narrow this down more.

Embraer 175 from below (picture source). I could not locate more than side views of the E 190, so an E 175 has to suffice here.

The prominent "bulge" on the bottom of the fuselage under the wing-- i.e. the way the wing-to-fuselage fairing is so prominent when seen from below-- also seems to be a relevant id feature.

I added the location, date and time.


text:
Can planes still land during a regionally-diverse ATC malfunction?
Spoilers for the Pilot episode of Scorpion

 In the Pilot episode for the TV series Scorpion, all major control towers in the greater LAX area are taken out because the firmware is malfunctioning and our heroes need to get a proper version active again, while the airborne planes could not be contacted through any method. They first try to recover a backup version of the software from a datacenter, but that fails. They then contact a salesman on a plane via his antique cellphone and manage to reload the software using a Ferrari and a laptop wired into the plane.
 One of the major plot points was that, because the software was malfunctioning, none of the planes could land safely, even though one of the planes could safely buzz the tower and even get close enough to the ground to make a wire connection to the ground. If they could fly so low, why can't they just land it?

So can a plane land during a complete control tower malfunction? And what is the general SOP in case of malfunctions? I've read both How realistic is the aviation crisis in the recent Spider-Man movie? and What happens to incoming flights when the airport shuts down, but part of the plot was that every airport in the greater LAX area got the problematic malware at the same time, so it's possible that many of those planes had their alternate destination airport also in trouble.

Aside from anything else, you can run ATC without a tower (that picture is USAF controllers after the Haiti earthquake; note the folding table replacing the tower)

@cpast That is the point of my question: I find it very difficult to believe that a pilot that can hover a commercial plane over a runway at less than 3 meters between the wheels and the tarmac is not capable of landing that same plane without the aid of ground personnel.

Even for a TV show, there are so many technical inaccuracies in the plot of that episode...

@digitgopher It would be easier to count the accuracies.  In fact, I can't find one in the spoiler.

@NateKerkhofs  You find it difficult to believe because it's so much nonsense.  You don't need any ground aids or personnel to land. Just an empty piece of tarmac/concrete long enough and wide enough.  The simple answer to your question is "yes".

Also, typical airport tower has three levels of backup for it's communication system. The first is basically similar to the primary system, the second is analogue radio with it's own generator and the third is a box of handheld, battery-powered analogue radios. There is no software in the later two. The communication is still plain voice radio that works on the same principle for almost hundred years and while new digital system is now being used in the busiest airspaces, the analogue one is not going away for foreseeable future, so it will always be there as a backup.

@Simon You'd probably need a bit more in LAX area so planes don't hit each other, though. It'd at least be a good idea to have a frequency where planes announce what they're doing to the other planes.

@Simon I found an accuracy! Salesmen tend to have cell phones, and it's generally possible to call people who are in a plane at low altitude.

During a control tower malfunction, can planes still land?

Yes.
If one tower goes down, the other layers of ATC will still be functioning, and they'll divert the aircraft elsewhere: if LAX goes down, national level ATC would work with the SoCal Tracon (Southern California Terminal Radar Approach Control -- i.e. "Approach") and perhaps the airline dispatchers to send the airplanes elsewhere: San Diego, Ontario, Long Beach, Burbank.  Those farther out would be diverted elsewhere just to avoid having too many airplanes piled up in one place: land in the Bay Area, or LAS or PHX, for instance.
Okay, let's assume that all the towers in the LA Basin are all down.  And let's assume that SoCal is down too.  And just to make the scenario complete, we'll assume that LA Center has lost all of their radios too.  (This is like the scenario that happened several months ago when Chicago Center lost their radios due to sabotage, except we're assuming LOTS of facilities all have the same problem at the same time.  Straining the limits of "willing suspension of disbelief" pretty hard here, but let's do it to make the point.)  What happens?
The pilots talk to each other on the usual frequencies and land.
There are plenty of uncontrolled airports out there, and they function just fine with pilots using what's known as CTAF -- the Common Traffic Advisory Frequency, where everybody broadcasts their position & intentions.  "Whozit Traffic, Cessna 1234A, left base, touch & go Whozit."  "Whozit Traffic, Piper 9876B, left downwind, full stop Whozit."  Based on those transmissions, you can build a good picture of who's where, who's closest to me & where I need to be looking to find him, and what (if anything) I need to do differently to not get too close.
And nobody needs ANY assistance from the tower in order to put the aircraft safely on the runway, stop, and exit.  We talk to them to keep the flow of traffic neat & orderly (they can be more efficient than just working it out on our own -- particularly when you start alternating departures with arrivals), but they have zero role in the actual act of landing.
Now in the scenario posited above where every ATC radio in all of the southern half of the state of California has failed, there would be complications, particularly if there was weather involved.  (See Die Hard 2, where weather had shut down EVERY airport in North America, apparently, save one, and the bad guys had shut down the ILS to that airport... we're well beyond "willing suspension of disbelief" there.)  But you'd also have a couple of things in your favor: no departures, and the runways normally used FOR departures would be available for landings as well.  Also, the goal is no longer a smooth & efficient flow of aircraft in & out; it's simply to get everybody on the ground safely.
Would it be a mess once you got on the ground & wanted to get to a gate?  Sure.  Visions of gridlocked LAX are easy enough to imagine.  But could everybody get on the ground safely?  Absolutely.

Once you're on the ground, you could probably just run a cop out to each plane with a radio, and put a radio in the control tower along with some sort of board to track where planes are. It's hard to use malware to mess with the fact that control towers are rather tall and have glass windows to see outside.

Or, honestly, one aircraft on the ground with a cell phone... tower says "tell AA123 to taxi north on A and hold short of B" on the phone, guy in the airplane repeats that instruction on the radio.  It'd work fine.  Not as efficiently as normal operations, and by the time you're out of gates & needing to push empty aircraft off the gate & take them someplace to park so that the stacked up airplanes can come in & unload, it will be a LONG day for a lot of people, but everybody's safely on the ground.

Not all airport actually have a control tower, so it is very much possible to land without any tower assistance.
On major airports however it would likely become chaos in very short time. In order to be able to communicate to aircraft in case of a radio failure, ATC control towers are equipped with light guns. These bright focussed lights allow an Air Traffic Controller to communicate instructions to aircraft both on the ground and in flight.

Yes it can(and that episode no matter how cool a show was full of simply non-accurate things). If your question is simply about a tower malfunction look for a minute at the fact that many airports (granted generally smaller ones) in this country do not have a control tower. They are thus called uncontrolled fields. You can find some nice guidance here on their procedures. Keep in mind these procedures are for uncontrolled fields there may be a different protocol for a large field losing its tower that I don't know about. On that note there are some fields that have towers that are not always operational be it seasonally or based on the hour of the day. In that event you can still land at the airport using uncontrolled procedures.
Now keeping that in mind there is an aircraft density issue at a place like LAX. Generally speaking uncontrolled fields are smaller and often less busy than a place like LAX so while it may not be "safe" there is nothing that would stop the planes from landing.


text:
How able were pilots of three-person cockpits at running the normal FE work?
This question is about whether a FE could fly solo.
I'd like to know to what degree the pilots could operate the FE console, e.g. if the FE was incapacitated. How much was covered as part of the type rating, and how much did they just pick up while flying?

First, these answers insofar as the licenses and airline operations apply to the U.S. system since that is all I am familiar with.
You must have a Flight Engineer license to operate as an FE. Just as a pilot's license has ratings on it, so does an FE license, and you have to have a rating that matches what you're flying. My FE license has a single rating, TURBOJET POWERED, so I could not sit as an FE in other than a jet aircraft.
In the days when 3-man cockpits were the norm, the usual career course at large carriers was to start out as an FE (second officer), progress to being an FO (first officer), and then a captain. In that system, if the FE was incapacitated, it was likely that one if not both of the pilots had actually been an FE.
The U.S military continued with FEs well after the 3rd seat came out of civilian aircraft (I think they still do, but am not sure). Military FEs were typically never intended to become pilots. When all new civilian aircraft being manufactured were 2-man cockpits, but lesser airlines were still flying the old 3-man cockpits (think freight carriers in particular), former military FEs became the source for their FEs and were considered professional FEs, in other words they would not be progressing to a pilot seat. A few did, but they were definitely the exception.
The two 747 carriers I worked for hired pilots into the FO seat. The FEs they hired had to have A&P licenses as well as an FE license, the reason being that the company wanted them to be able to perform and sign off minor maintenance problems that occurred in remote places (think Africa especially) where maintenance wasn't locally available. With only a couple of exceptions, every FE I ever flew with was ex-military with an A&P, and they knew the airplane mechanically better than I.
In the airline ground schools, especially the initial groundschool, the FE panel and its operation were thoroughly covered in the material presented and in the testing. The oral exam for the aircraft type rating thoroughly covered that FE panel. As I remember my 747 type rating oral was 3 to 4 hours long. Fortunately I got through that and the sim ride on the first try. Not all do.
So, in the case of an incapacitated FE in the 10 years I was on the 747, it was likely that neither pilot had actually operated as an FE. However, he would have studied it in ground school and had demonstrated an understanding in an oral exam. There is, though, nothing like experience and currency.
Every once in awhile I would get out to a cold airplane before the FE had arrived and would want to start the APU. This was usually at a remote station without local maintenance. There was, of course, a procedure for doing this, and I had a copy. But even with that check list and doing everything very carefully, I always breathed a sigh of relief when the APU started and there were no problems. If the APU failed to start on the first try, I usually waited for the FE to arrive. I might try a second time if I knew he was going to be awhile, but never a third.
The old 747-100/200 had a lot of switches, and interesting things could happen if the APU was started and the switches were not properly set. I always did an outside check to make sure all gear doors were closed and that nobody was around the bottom of the airplane. If a gear door was down, and switches were not set right, when the APU started, the doors would immediately close when the hydraulics were pressurized. Anyone in the way would certain get hurt.
Individual pilots on the line varied greatly in their knowledge of the FE panel. FOs were at a disadvantage insofar as watching it be operated. They can't see it well. Captains can see it. However, some FEs resented captains looking at it too much, feeling that was their turf. What I often did during cruise, as much to pass the time as learn, was to let the FE be my tutor.

Does the FE rating differentiate between turbojet vs turbofan?

@vasin1987 They didn't back when I got my FE license. A quick Google search turned up http://www.airlinerdispatch.com/flight-engineer-requirements.html, which seems to indicate they still don't in that the three ratings listed are (1) Reciprocating engine powered;
(2) Turbo propeller powered; and
(3) Turbojet powered


text:
Is the "confirmed allocation" string in "A Scandal in Belgravia" a real airline practice?
(This is a repost of this question on Movies SE. I hope to get better answers here.)
Irene Adler shows the following text to Sherlock:
007 Confirmed allocation
4C12C45F13E13G60A60B61F34G34J60D12H33K34K

He immediately guesses that "these are seat allocations on a passenger jet", claims it must be a Boeing 747 and then recalls a specific flight which takes off at 6:30 PM the next day. Note that only 14 seats are listed. A Boeing 747 can carry about four hundred passengers. The flight takes off tomorrow evening.
Do airlines really document or communicate seating allocations in this way? Shouldn't there be more seats "confirmed" (whatever that means)?

there's a seat J which means that the row contains at least 10 seats and a row 60 (making for a 60*10 possible seats), though how they are setup is specific tot he airliner

@ratchetfreak: Yes, that was in the movie. But what is that string typically used for and why are so few seats confirmed?

maybe other seats were confirmed before and these were late buyers

@ratchetfreak: Well, perhaps. That's why I ask here and hope that someone who knows airline operations in great details can explain it.

I edited the question to try to 'salvage' it, but I personally feel it's off-topic. Even if this isn't just a writer's invention and airlines really do document seat allocations like this (unlikely), it's not aviation as such, just data handling.

@ratchetfreak - that doesn't necessarily mean 600 seats: some aircraft may use ABC DEFG HIJ, others may use AC DG HJ (in order to preserve the A/J window seats, CD GH aisle seats). There are often a large number of missing rows, and First/Business class will have much fewer seats per row

No
Based on my research for string confirmed allocation, there were no references found related to airlines or their practice.
However, the background scenario about the conversation Sherlock was having, something like the following had happened (references: this and this and this and this and this):
(my paraphrasing, not actually a quote)

Sherlock knows that 007 is a flight of Bond Air which is leaving for
  Baltimore tomorrow at 6:30pm. He is aware of a terrorist plot of
  having dead bodies on an airplane (14 seats allocations) so that no one actually dies. The
  first 0 in flight number indicates that zero causalities will happen.

P.S.: This question is not about aviation but movies.